This invention relates to heat exchangers of the type formed of stacked plates, wherein the plates have raised peripheral flanges that co-operate to form an enclosure for the passage of heat exchange fluids between the plates.
The most common kind of plate type heat exchangers produced in the past have been made of spaced-apart stacked pairs of plates where the plate pairs define internal flow passages therein. Expanded metal turbulizers are often located in the internal flow passages to increase turbulence and heat transfer efficiency. The plates normally have inlet and outlet openings that are aligned in the stacked plate pairs to allow for the flow of one heat exchange fluid through all of the plate pairs. A second heat exchange fluid passes between the plate pairs, and often an enclosure or casing is used to contain the plate pairs and cause the second heat exchange fluid to pass between the plate pairs.
In order to eliminate the enclosure or casing, it has been proposed to provide the plates with peripheral flanges that not only close the peripheral edges of the plate pairs, but also close the peripheral spaces between the plate pairs. One method of doing this is to use plates that have a raised peripheral flange on one side of the plate and a raised peripheral ridge on the other side of the plate. Examples of this type of heat exchanger are shown in U.S. Pat. No. 3,240,268 issued to F. D. Armes and U.S. Pat. No. 4,327,802 issued to Richard P. Beldam.
A difficulty with the self-enclosing plate-type heat exchangers produced in the past, however, is that the peripheral flanges and ridges form inherent peripheral flow channels that act as short-circuits inside and between the plate pairs, and this reduces the heat exchange efficiency of these types of heat exchangers.